Tuesday, April 9, 2013
Snow doesn't slow down ruffed grouse
Snow that’s deep enough for skiing, snowshoeing, snowmobiling -– and swearing -– covers much of Wisconsin as we trudge out of March, but while wintery Aprils can plague white-tailed deer, they don’t faze ruffed grouse.
That’s especially true if the grouse can bury themselves in snow overnight for protection from predators and cold temperatures. Ruffed grouse, after all, are the Eskimos of the bird world. But instead of building shelters from blocks of snow cut with saws and shovels, grouse simply dive head first into snow banks to end a flight, or stand atop the snow and shuffle in place until submerged.
Those entry techniques become difficult as snow melts, freezes and compacts, but as long as it’s 8 inches or deeper, grouse usually make it work. Still, they prefer light, deep and fluffy snow, which is seldom a problem during North Woods winters.
My friends and I often find the grouse’s abandoned snow roosts in Ashland County while hunting deer season in late November and early December, or when snowshoeing in February. No matter the roost’s construction, we always stop to investigate, maybe because bird architecture never loses its interest.
Sometimes snow roosts are just softball-sized potholes with grouse tracks leading away. Other times they’re flanked by matching wingtips in the snow where grouse launched themselves from shallow caves.
Still other snow roosts –- called “kieppes” -– link to a collapsed tunnel. A closer look at the tunnel’s far end usually reveals the bird’s entry point. Grouse burrow the horizontal tunnel in between for one to three yards before settling into their overnight roost.
Biologists assume grouse dig these short tunnels to disguise their roosts from foxes, coyotes and bobcats, much as cottontails do when building snow tunnels to their burrows. That’s probably a safe assumption, but there’s no doubting the thermal protection of the roost itself.
There’s been lots of research into the ruffed grouse’s “thermal energetics.” That’s the temperature where grouse must increase their metabolism and body heat to maintain proper functions.
When must grouse start burning extra energy? Well, some experts say it’s 40 degrees and other say it’s 28 degrees. Either way, ruffed grouse are built for harsh winters, and that means surviving temperatures far colder than the 30s.
Scott Walter, the Department of Natural Resources’ upland ecologist, said when he was conducting research with students at UW-Richland Center before his DNR days, he calculated that grouse roosting beneath snow burned 2.5 times less energy than those roosting above it.